There are various reasons why a marriage might break down. Common reasons include adultery or continuous arguing. Some couples are unable to work through their problems.
Buddhist monks or nuns may themselves have been married prior to ordination and so can often combine religious with practical advice to people who come to them to discuss problems. Like other religious professionals, they can also accumulate over the years a lot of knowledge from their congregation which they can pass on to people who are experiencing difficulties.
Married people who want to separate and divorce will always be advised to proceed with as much harmony as possible, both for the sake of their families and children, but also for their own sake. It will only hurt them if they get very angry and resentful. It will be easier for each person if they try to feel compassion for their partner.
Buddhists may also choose to divorce in order to reduce suffering and to help achieve enlightenment. They may also choose to remarry – a way of finding happiness again and reducing suffering in their lives.